Automated dispenser

ABSTRACT

An automatic dispenser for dispensing lengths of paper for use as hand towels, includes an IR sensor system for detecting a user. The sensor system scans at a first scanning rate and also at a second higher scanning rate. When the sensor system detects a user, it changes the scanning rate from the first to the second rate. The dispenser aims at reducing power consumption while providing improved reaction time when required to dispense paper.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of international application PCT/EP2005/007617filed on 13 Jul. 2005, which designated the United States of America.

FIELD OF THE INVENTION

The present invention relates generally to a dispenser, in particular ofthe type including a motor-driven dispensing system combined withcontrol circuitry for sensing the presence of a possible user andcontrolling operation of said motor to effect dispensing of material.The invention furthermore relates even more particularly to an automatictowel dispenser (preferably paper towels stored inside the dispenserhousing) of the electrically powered type (particularly of the DCbattery powered type, but which may also be an AC-powered type or acombination of AC and DC power types) in which paper sheets such aspaper hand-towels are dispensed when the presence of said possible useris detected to fulfill the condition of being within a specified zone,without physical contact of the user with the dispenser being necessaryfor initiating the dispensing sequence. Such dispensers are oftenreferred to as hands-free dispensers or touchless dispensers.

BACKGROUND OF THE INVENTION

Dispensers of the aforementioned type are known for example fromUS-A1-2003/0169046 and U.S. Pat. Nos. 6,695,246 B1 and 6,069,354.

In for example the dispenser according to U.S. Pat. No. 6,695,246 B1,the sensor control circuitry uses either passive infrared (IR), i.e.detection of reflected ambient IR, or active IR (both IR emission anddetection) to control sensing of the presence of a possible user. In theactive IR mode the presence of an object (i.e. a possible user) can bedetected within a detection zone of about 12 to 24 cm from the dispenserand upon said detection operates a motor to dispense a hand towel to auser. The detection zone is kept small so that objects which are outsidethe detection zone do not lead to undesired and unintentionaldispensing. When in the desired zone, the microprocessor controlling themotor operation only activates the motor to dispense a towel when twoscans are received by the IR sensing circuitry. The microprocessor canbe operated to scan at about 7 Hz (i.e. 1 scan each 0.14 seconds) byusing an oscillator to turn power to the microprocessor on and off.Alternatively, it can be set to operate at a different frequency. Whenthe motor is operating the microprocessor is kept on constantly.

US-A1-2003/0169046 discloses a dispenser in which an IR sensing systemis mentioned as an alternative to capacitance detection for proximitydetection. In an example of capacitance-type sensing the capacitativetype sensor is connected to a microprocessor. No details are given as towhere an IR sensing system, if present, would be located, nor how itwould be arranged to operate. A further sensor system is included fordetecting paper web in a discharge chute. This further sensor system forthe paper uses the microprocessor to pulse power on/off to opticalsensors. Additionally, a watch-dog timer can be used which closes downthe pulsing function and resumes it again when it periodically wakes themicroprocessor from sleep mode.

U.S. Pat. No. 6,069,354 discloses a dispenser using active IR whichgenerates a square wave at about 1.2 kHz so as to emit a modulated IRsignal, which is detected by reflection against a possible user to an IRdetector. This document proposes using a sensor system set to sense auser between about 1.25 cm and about 30 cm distant from the dispenser.

The aforementioned documents all use sensor systems which, when active,operate at a specific scanning rate (frequency) to operate a motor todispense a piece of towel.

The aforementioned dispensers operate by using a scanning rate (numberof scan per second), which is fixed when the device is active. This rateis kept fairly high so that when a user is in a detection zone, thedispenser will not take too long to dispense. This high scanning ratemeans however that power is being consumed at a high level since the IRemitters and detectors need to be activated very often and these consumepower when active. Using a lower scanning rate would of course savepower, but the time to dispense a towel would then be longer, and whenthe user moves his/her hands towards the dispenser rapidly afterwashing, this can give the impression to the user that the device is notdetecting him/her properly if a towel is not dispensed immediately.

The present invention has as one of its objects, the provision of lowpower consumption by the sensor system in periods when apossible/potential user (i.e. an object assumed to be a user requiringdispensing of a product such as a length of hand towel or toilet paper)is not located near enough to the dispenser, and at the same time toprovide a relatively quick reaction time when a possible/potential useris near enough to the dispenser and needs a towel to be dispensed. Lowpower consumption is particularly important in dispensers which areentirely battery powered by one or more replaceable batteries,especially those battery systems that operate without a rechargingpossibility by a solar cell recharging system or other type ofrecharging system, as dispensers of this type are generally expected tooperate for a long time (e.g. enough time to dispense 60 or more rollsof paper without requiring battery replacement).

A further object of the invention is to allow still further power savingwhen there are no possible users in the vicinity of the dispenser.

Still further objects of the invention will be apparent on reading thisspecification.

SUMMARY OF THE INVENTION

The main object of the invention is achieved by the dispenser having thefeatures defined in the independent claim. Certain preferred features ofthe invention are defined in the dependent claims.

Further preferred features of the invention will be apparent to thereader of this specification.

The invention is based on the idea that the scanning rate, i.e. thenumber of scans performed per second, is made to vary upon the locationof a user with respect to the dispenser, such that the dispenseroperates at a first scanning rate (i.e. performs a scanning sequence byactivating IR emitter and receiver circuits, and emitting singlescanning pulses at a first number of single scans per second) when nopossible/potential user is detected. The system then increases thescanning rate when a user is considered to be close to the dispenser(i.e. has entered a first detection zone). This variable scanning rateallows very low power to be used when no users are adequately close tothe dispenser, and only to use a higher power level when required, sothat a quick reaction time to dispense a product is experienced by theuser.

The invention thus provides a sensor system that creates a firstdetection zone which, when entered by a possible user, causes thescanning rate to change from a first lower scanning rate to a secondhigher scanning rate.

The first detection zone can be varied in size so as to detect a user atvarying distances. For example, a remote sensor linked by either a wireconnection to the dispenser or by a wireless link (e.g. IR or radio) tothe dispenser can be used to detect a user entering a washroom and thuscan cause the first scanning rate to change to the second scanning rate.Such a “remote” sensor could, if desired alternatively be mounted on thefront-facing portion of the dispenser and can be arranged to operate ata very slow scanning rate due to the distance of the entry to a washroomfrom the location of the dispenser, such that by the time the possibleuser wishes to use a dispenser and has thus moved closer to thedispenser, the dispenser is already operating at a higher secondscanning rate.

Alternatively, the same set of sensors which are used to cause thedispenser to dispense a product can also be used to detect a userentering a first detection zone and to include a control system whichchanges the scanning rate from the first slower rate to the secondhigher rate. In this way, a user approaching the dispenser (e.g. 40 to50 cm or perhaps further away from the dispenser) will activate thesensor system to change the scanning rate to a higher scanning rate andas the user continues to move his hands and/or body closer to thedischarge outlet of the dispenser, the user will be detected as being ina “dispensing zone” and will thus cause the dispenser to dispense aproduct (e.g. a paper hand towel).

If desired, more than two scanning rates can be used. For example afirst slow scanning rate can be used (such as 1 or 2 times per second)followed by a higher second scanning rate (e.g. at 3 to 6 times persecond), followed by a further higher rate (e.g. at 7 to 12 times persecond), whereby the scanning rate is increased from one rate to thenext as the user is detected to be moving closer to the dispenser. Thiscan be performed by a series of different sensors for example, eachdetecting at different distances, or for example by using the same setof sensors detecting an increased IR signal reflection from the user asthe user approaches closer to the dispenser.

When a user moves away from the dispenser, the scanning rate can then bedecreased again to a lower rate, thereby consuming less sensor operationpower.

As will be apparent, even at relatively short distances for the firstdetection zone (e.g. up to about 50 cm from the dispenser for example ina 30° to 60° slanted forwards and downwards direction) it will beunderstood that the system has significant power saving advantages whilestill allowing a good reaction time to dispense a towel. This is becausethe user expects to move his/her hands relatively close to the device inorder for dispensing to occur, and this takes on the order of between aquarter and half a second at normal hand movement speeds (between 0.2m/s and 0.5 m/s), by which time the dispenser can be made to be alreadyscanning at the second higher rate (or even a still higher rate) andthus be able to dispense very close to the time when the hands are in an“expected” position for dispensing (i.e. a position at which the userwould expect a towel to be dispensed, typically some 15 to 25 cm fromthe dispenser outlet).

Likewise, it is preferred that when using an IR sensor system, thesensor system should preferably be able to cope with singular anomaliesof short term high IR reflections, as sometimes occurs, withoutdispensing a towel, so that it is appropriate to sense two or moreconsecutive scans, or e.g. a predetermined number of scans in a numberof consecutive scans (e.g. two out of three consecutive scans), eachbeing at a predetermined level of IR above background level, beforedispensing a product.

Advantageous use can be made of the varied scanning rate by making thefirst scanning rate between e.g. 0.15 and 0.25 seconds between scans(i.e. the scanning rate when a possible user is outside the firstdetection zone), or even longer (such as between 0.25 and 0.5 seconds),and the second scanning rate of the order of about 0.08 to 0.12 secondsbetween scans and requiring only two consecutive scans (or e.g. two outof three consecutive scans) providing a reflected IR level abovebackground IR level to activate dispensing. Such dispensing will beperceived by the user as almost immediate, yet a significant amount ofpower used by the sensor system can be saved due to the initial lowscanning rate which consumes less power.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail with reference tocertain non-limiting embodiments thereof and with the aid of theaccompanying drawings, in which:

FIG. 1 shows a schematic front view of a paper towel dispenser with apaper roll and paper transport mechanism in hidden view, depicting afirst detection zone,

FIG. 2 shows a side view of the arrangement in FIG. 1 whereby a sidepanel of the dispenser has been removed to show schematically the paperroll and simplified schematic details of the paper transport mechanism,

FIG. 3 shows a further embodiment of the invention with a further sensorable to detect a user at a further distance from the dispenser,

FIG. 4 shows an exemplary plot of emittance amplitude of the scanningpulses against time,

FIG. 5 shows a plot of received signal level against time, for a seriesof received IR reflections occurring due to the emitted IR pulses inFIG. 4,

FIG. 6 shows a block diagram of the basic system elements of anembodiment of a dispenser according to the invention,

FIG. 7 shows an RC circuit used for effecting wake-up of themicroprocessor in the MCU so as to perform a scan, and

FIG. 8 shows an alternative version of the RC circuit depicted in FIG.7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 and FIG. 2 show a dispenser 1 in front and side viewsrespectively, whereby FIG. 2 shows the dispenser 1 attached at its rearside to a wall (the means of attachment are not shown but may be of anysuitable type such as screws, adhesive, adhesive tape, or otherattachment means).

The dispenser 1 comprises a housing 2, within which is located a productsupply, in this case a supply of paper in a roll 3. The roll is suitablya roll of continuous non-perforated paper, but may also compriseperforated paper in some cases. Also located in the housing 2 is a papertransport mechanism 4, preferably in the form of a modular drivecassette with its own casing 15, which can preferably be removed as asingle unit from the housing 2 when the housing is opened.

FIG. 1 shows the paper roll 3 and the transport mechanism 4 as simpleblocks for the sake of simplicity. Likewise, FIG. 2 shows the paper roll3 and the transport mechanism 4 in a vastly simplified form, whereby thetransport mechanism includes a drive roller 5 engaged with a counterroller 6, whereby a portion of the paper sheet 7 is shown locatedbetween said rollers 5, 6, with the leading edge of said paper sheet 7ready to be dispensed at a discharge outlet 8 formed in the housing 2 atthe lower side thereof.

The drive roller 5 is shown schematically connected to an electricaldrive motor M powered by batteries B. A gearing, typically in a gearbox,may be included between the motor drive shaft and the drive roller 5.Suitable batteries may supply a total of 6V when new and typically four1.5V batteries are suitable for this purpose. Exemplary of suitabletypes are Duracell's MN1300 batteries, whereby each battery has acapacity of 13 Ah and which can operate from full to total dischargebetween the range of 1.5V to 0.8V. Operation of the motor M causes driveroller 5 to rotate and to thereby pull paper sheet 7 from the paper roll3 by pinching the paper between the nip of the rollers 5 and 6. Uponactuation, the motor rotates, thereby withdrawing paper sheet from theroll 3, which also rotates so as to allow paper to be moved towards thedischarge opening 8. Other forms of drive mechanisms for withdrawingpaper from a roll may also be used. The details of the paper transportmechanism or other product transport mechanism are however not importantfor an understanding of the invention. Such devices are also well knownper se in the art.

It will also be understood from the foregoing that drive roller 5 andcounter roller 6 may have their functions swapped such that the counterroller 6 could be the drive roller which is operably connected to thedrive motor (and thus the drive roller 5 depicted in FIG. 2 only acts asa counter roller in contact with roller 6, normally with paper or towelin the nip therebetween).

Although the principle of operation is explained using paper in the formof a continuous paper sheet in a roll, it is to be understood that thedispenser may be used to dispense other products from a product supply,such as a continuous piece of paper in concertina format for example.Alternative products may be dispensed by the device with appropriateredesign thereof. It is also possible that other dispensing devices aretagged on to the dispenser. For example, the dispenser may furtherinclude an air freshener which is activated for example once every 5 or10 minutes (or other suitable time) or once upon a certain number oftowels dispensed. This extra tagged-on dispenser can be controlled bythe dispenser control circuitry (to be described below) or by separatecontrol circuitry (not described herein).

The motor M is at rest and without power applied to it when no paper isto be dispensed. The motor M is rotated when paper is to be dispensedthrough the discharge opening 8. The operation of the motor M iscontrolled by a master control unit (not shown in FIG. 1 and 2, butdescribed below) connected to a sensing system comprising sensors 9-13,of which sensors 10 and 12 are emitters, preferably IR emitters, andsensors 9, 11, and 13 are IR receivers. Such IR emitters and receiversare well known in the art and typically comprise diode structures.Suitable IR emitters and receivers are for example made by Lite-ONElectronics Inc., under Type number LTE-3279K for the IR emitters andunder Type number LTR-323DB for the receivers. Other types of IRemitters and receivers may also be used of course. In the shownembodiment, the IR emitters 10, 12 and IR receivers 9, 11, 13, are shownapproximately equally spaced consecutively in the lateral direction X-Xof the housing (generally parallel to the product supply roll 3). Thespacing can suitably be about 5 cm spacing between a consecutive emitterand receiver, such that the distance between sensors 9 and 10, 10 and11, 11 and 12, 12 and 13 are all approximately equal.

Also, the emitters and receivers are shown (see FIG. 2) placed onopposite sides of the discharge outlet 8. Other arrangements of sensorsare also possible such as where all sensors are placed on the front sideof the outlet in a straight row (i.e. at the location where sensors 10and 12 are shown to be placed in FIG. 2). Sensors could also be placedon the rear side of the outlet in a straight row (e.g. where sensors 9,11, and 13 are shown to be placed). An arrangement of sensorsconsecutively in a row in the orderreceiver/emitter/receiver/emitter/receiver allows an advantageous shapeof detection zone, which is somewhat tongue-like in shape (see FIG. 1).The underlying tongue shape can be altered somewhat depending on powerapplied to the emitters and also their relative extent of protrusionfrom their housing for example.

The dispenser 1, upon detection of a possible user (the detectionprocess being described further below) without any contact of the userneeding to take place with the dispenser or the sensors, for asufficient time in the first detection zone, thus causes the dispenserto determine that a user is present in a dispensing zone and thus todispense a product. Dispensing is performed in this case by the frontportion of the paper 7 being discharged automatically. This allows theuser to grasp the paper 7 and to draw it against a cutting edge such ascutting edge 16 shown in FIG. 2, proximate the discharge opening 8, soas to remove the torn/cut-off piece of paper. The location of thecutting edge may be varied of course, such as to be at the level of, orup to 1 cm below, and opposite to the roller 5.

The first detection zone 14 as shown in FIG. 1 and 2 is shown assomewhat tongue-like and is inclined downwardly and forwardly of thedischarge opening at an angle x° of preferably between 20° to 30° to thevertical axis Y, for example 27.5° As will be explained below in moredetail, when a part of a possible user's body enters this firstdetection zone 14, the sensing system detects the user's presence andcauses the sensor system to change from a first scanning rate to asecond scanning rate which is higher than said first scanning rate. Thesensing system also then causes the motor M to turn upon regarding auser (due to the signals received) as being present in a dispensingzone. The determination of a user being in a position requiringdispensing of a towel is explained below.

While a preferred form of the emitter/receiver arrangement isadvantageous, the use of only one emitter and one receiver can also beused, or more than 2 emitters and 3 receivers. The pattern or fieldcovered by the sensors will however vary accordingly and 2 emitters andthree sensors has been found to be advantageous from the balance betweenthe coverage area obtained and the power consumption required.

In an alternative embodiment shown in FIG. 3, a further sensor 19,remote from the dispenser housing 2 and operatively connected bywireless or wire connection 20 to the sensor system (shown schematicallyat 22) and its control system in the dispenser housing, may be used toform a first detection zone 18 which is further from the dispenser thanthe detection zone 17 (detection zone 17 in this case is similar inshape to the first detection zone 14 in FIGS. 1 and 2). Alternatively oradditionally, a further sensor may be placed on the front part, e.g. afront surface, of the dispenser housing and facing forwards away fromany wall or the like on which the dispenser is mounted, to allow alonger range of detection forwards of the dispenser, such as the sensor21 shown schematically which is likewise connected to the sensor system22. The sensor 19 and/or 21 may for example be arranged to detect thepresence of possible users up to a distance of more then the firstdetection zone, e.g. a distance of more than 50 cm, preferably more than100 cm, more preferably more than 200 cm and still more preferably morethan 300 cm or even further from the dispenser housing 2.

The emitters 10, 12 of the sensor system are arranged via suitablecontrol circuitry, which may control circuitry as known per se in theart, to emit pulsed IR at a narrow frequency band of about 15 kHz.Another IR frequency could however be chosen. The receivers 9, 11, 13,are arranged to detect the emitted IR which is reflected against objects(stationary or moving) back towards the receivers, In order to detectthe IR which initiates primarily and almost entirely from the emitted IReven up to very strong lighting conditions (10 000 lux or more), ratherthan all sources and frequencies of IR radiation due to backgroundinfluences, the IR receivers need to be tuned to the frequency of theemitters. Thus the IR receivers are provided with a detection circuitwhich suppresses IR outside the expected frequency range of thereflected waves and amplifies the IR at the 15 kHz range level. In thisregard, while a frequency detection range both above and below theemitted frequency band range of between 2 to 10 kHz can operate in mostsituations, it has been found more suitable to use a frequency range(frequency band) which lies about 3 kHz above and also below the centralfrequency of the emitted IR. Thus, the receivers are tuned (or in otherwords “synchronized”) with the emitted IR (at a central frequency of 15kHz) by allowing IR in the range of 12 to 18 kHz to be detected (e.g. byuse of a band pass filter set at 12 to 18 kHz). Frequencies outside thatband are thus heavily suppressed, while the frequencies within the 12 to18 kHz band are amplified, with maximum amplification being at thecentral frequency of 15 kHz, up to for example about 53 dB.

By operating with a modulated frequency in the emitters and receivers,the effects of e.g. bright sunlight which might otherwise causesaturation of the IR received signal compared to any reflected signalare substantially obviated allowing the device to work in lightconditions of up to about 10000 lux background illumination.

FIG. 4 shows a series of individual scans (i.e. a pulsed IR emission) ata first scanning rate having a time between individual scans of t1, asecond scanning rate having a time between individual scans of t2 whichis shorter than t1 (i.e. a higher scanning rate than t1) and a thirdscanning rate having a time between individual scan of t3 where t3 isgreater than t1 and t2. The time between individual scans is measured asthe time from the start of one single scan to the time of starting thenext individual scan. Each of the individual scans is here shown ashaving the same pulse intensity (i.e. no adjustment is made betweenindividual scans to take account of previous received reflected scanswhich may result in a different emittance power being supplied to the IRemitters. A further time t4 is shown which is a predetermined time or apredetermined number of pulses separated by time t1 (the first scanningrate) which needs to elapse before the system alters the scanning rateto the third, slowest scanning rate with time interval t3. The pulsewidth of each individual pulse is normally constant.

The time t1 is set at a constant level to lie between 0.15 to 1.0second, preferably 0.15 to 0.4 of a second, i.e. such that eachindividual scan pulse is separated by an equal time t1. The time t1 canhowever be varied and a very suitable rate to optimize the device forbattery power saving and reaction time to dispensing has been found tobe about t1=0.17 seconds. The second scanning rate is always faster thanthe first scanning rate and t2 is set to lie preferably between 0.05 to0.2 seconds, most preferably between 0.08 and 0.12 seconds betweenscans. The time t2 can however be varied to be another suitable value,but preferably lies between 30% to 70% of t1. Time t3 may be set at forexample between 0.3 and 0.6 seconds, although a longer time t3 is alsopossible, such as 1 second or even longer. However, for emittancecircuit time triggering (in particular by using an RC triggering circuitusing the RC time constant to cause a discharge of current to themicroprocessor for initiating timing operation), it is most suitable ift3 is set to double the length of t1. Thus, t3 may be set at 0.34seconds in the case when t1 is 0.17 seconds. The initial time t1 can bemade variable, for example via a variable resistor operated from outsidethe device, although typically this will be factory set so as to avoidunintentional alteration of time t1 which is unsuitable in certainsituations.

Time t4 may typically be chosen to be of the order of between 30 secondsto 10 minutes and may also be variably set up in the device dependent onthe type of use and surroundings which are normally encountered wherethe device is to be located. A suitable value for optimized operationhas however been found to be about 300 seconds although may also bemore, where it is desired to save further power.

Although not shown, it will be apparent that additional time periods mayalso be set in the device with intermediate time periods (i.e.intermediate between the values of the t1 and t2 values, or intermediatebetween t2 and t3 etc) or even greater time periods, dependent onoperating conditions, although the use of three different scanning rateshas been shown to take account of most situations with good performancein terms of reaction time and power saving. For example a further timeperiod longer than t4, e.g. 30 minutes, occurring during issuing ofscans at interval t3 could be used so as to alter the time periodbetween scans to be longer than t3 (e.g. 10 seconds between individualscans). Such a situation may be useful when the dispenser might nothardly be used for night-time periods. The reason for this will becomeclearer upon reading the following description of operation.

As can be seen in FIG. 4, after four scans S1-S4 at a time interval oft1, the scanning rate changes to the second faster scanning rate withinterval t2 and continues at the second scanning rate for two furtherscans S5 and S6. The reason for this change will be explained below withreference to FIG. 5.

FIG. 5 shows a sample of the possible received signal level (receivedsignal strength) of the received signals R1-R7 caused in response toemitting the scan pulses S1-S7.

The approximate background IR level is indicated as a signal receivedlevel of Q0. This level Q0 may of course vary and as shown further belowthis can however be taken into account. For simplicity of explanationhowever, it is assumed in the following example that Q0 remainssubstantially constant.

When S1 is emitted and there is no object which is not accounted for inthe last background value of received signal, the background levelreceived at R1 will be approximately at level Q0. Likewise at the nextscan S2 the level of IR received is also close to Q0 and thus causes noalteration of the first scanning rate. At scan S3, the received signallevel R3 is however above background level, but only marginally (e.g.less than a predetermined value, for example less than 10%, abovebackground IR level) and thus the first scanning rate is maintained.Such small changes, (below the predetermined level) above and below Q0can occur due to temporary changes in moisture levels or persons movingat a longer distance from the dispenser, or stray IR due to changes insunlight conditions or temperature conditions around the dispenser.

At scan S4, the received signal level has reached or surpassed thepredetermined value, of e.g. 10%, above background IR and the sensorsystem and its control thus assumes that a possible user (e.g. theuser's hands or whole body) is moving closer towards the dispenser inorder to retrieve a product such as a paper towel. In order to be ableto react faster when the user is assumed to wish that a towel to bedispensed (i.e. when the received signal level has reached or surpassedthe predetermined value of e.g. 10% above background IR), the scanningrate thus increases to the second scanning rate and thus issues the nextscanning pulse at a shorter time t2 after the previous pulse.

If the signal level R5 received on the next scan S5 also fulfils thecriteria of being at, or more than, a predetermined level abovebackground IR (e.g. at or greater than 10% above background IR inaccordance with the criteria used for the previous scans), the sensorsystem records via a counter (e.g. in a memory or another form ofregister) a single detection above the predetermined level, and thenissues a further scan S6 at interval t2 to check whether the received IRis still at or above the level of e.g. 10% greater than background IRQ0. As shown in FIG. 5, this is the case for scan S6, and the sensorsystem control (comprising both software and a microprocessor in apreferred form) then immediately issues an output to the motor M tostart the motor turning in order to dispense a product (e.g. a portionof paper 7 from roll 3). In this case, i.e. when two consecutive scansare above the predetermined level, the system has thus determined that apossible user is in a zone requiring a product to be dispensed, and thusdetermines that the user is in a “dispensing” zone.

In the case where only one set of sensors is used to detect the presenceof a user in the first detection zone (e.g. the embodiment of FIGS. 1and 2), the detection zone and the dispensing zone will be the samephysical zone, but it is merely the sensor control system whichlogically determines that a user has entered the dispensing zone.

In the embodiment of FIG. 3 however, where an additional sensor 19and/or 21 is used, the signal level R4 will have been sensed in zone 18and thus will already have caused the first scanning rate to change tothe second scanning rate before the user has entered zone 17 which, inthe case of FIG. 3, would be the dispensing zone which is distinct thefirst detection zone 18. The zones 17 and 18 could of course overlap toa lesser or greater degree, but zone 18 in such a case should alwayshave at least a portion thereof which is arranged to extend further fromthe dispenser than zone 17. In such a case it is however appropriate forthe second scanning rate to be maintained for a time suitable for a userto physically enter the zone 17 (e.g. a time for moving towards a washbasin, washing hands and then using a towel). Such a suitable time maybe set for example between 1 and 10 minutes, during which time thesecond scanning rate is maintained, in the expectation of receiving IRreflected signals R which fulfill the criteria that a product is to bedispensed.

In a further situation, not shown, where the level at R5 is below thepredetermined level (e.g. 10% above background IR), the system may beprogrammed to issue a further scan and to check again whether thereceived signal level is at or above the predetermined level so as toindicate that a user is present and wishes to receive a towel. Thus,rather than always requiring two consecutive scans to produce tworeceived signals having a received signal strength above thepredetermined level, it has been found preferable to allow any two ofthree consecutive scans to be above the predetermined level. Furtherpossibilities also exist of course whereby the number of scans to allowdispensing of a towel could be any two out of four consecutive scans, orany three out of four consecutive scans, or further combinations.However, with t1 set at 0.17 seconds and t2 at 0.1 seconds, it has beenfound suitable to allow any two out of three consecutive scans totrigger dispensing of a product as this produces very reliable results.

In the case shown in FIG. 4, after a towel or other product has beendispensed (discharged), the system alters the scanning rate back to thefirst scanning rate so as to save power, and thus scan S7 is emitted attime t1 after scan S6. Clearly, this saves power as early as possible.However, the second scanning rate can be maintained for longer ifdesired (situation not depicted in FIG. 4) so that when a user againwishes to take a second or further product (e.g. a further towel) bymoving their hands again towards the dispenser outlet, the dispensingoccurs quickly again.

In the case shown in FIG. 5, a case is shown corresponding to FIG. 4,where the user has for example torn off a piece of paper which has beendispensed from the dispenser and thus the level of IR radiation receivedat R7 has moved back below the predetermined level (e.g. below apredetermined level of 10% or more above Q0).

The predetermined level above background level at which the sensorsystem control causes discharge of a product to occur has been describedabove as being 10% above background for two out of three consecutivescans. However, practical tests have shown that a more suitable level isat or above 12% greater than background IR, and even more preferably ator above 15% greater than background IR. This is for example to takeaccount of varying light conditions which may occur when a user is closeto the dispenser, but not actually wishing to use it.

However, it has also been found in testing that the increase inreflected IR which is received allows entirely different thresholds tobe used where desired. Thus for example the sensor circuits can be tunedsuch that the predetermined level above background level is up to 90% ormore, even up to 95% or more, above background IR, before dispensingoccurs. This allows for example a far greater distinction of thereflection from a user's hands compared to any non-desired received IRin the pulsed bandwidth of 12 to 18 kHz (e.g. in the case of very stronglight conditions). At the same time, the proximity at which such a highlevel occurs is generally less than when a lower predetermined level isused, unless the current to the emitters is slightly increased.

In some cases, users may move their hands very quickly towards thedispenser and may be aggravated by having to wait for a time more thanabsolutely necessary for the first scanning rate to alter to the secondscanning rate and wait a further 0.2 seconds (when using t2=0.1), eventhough this in most cases is a negligible time. A further overridingcontrol may thus be included in which any single received scan signal ator above e.g. 30% (or a higher amount, such as above 95% in the casedescribed in the preceding paragraph) compared to background level canbe used to cause immediate dispensing of a product, without requiringconsecutive scans at or above a predetermined level, even when in thefirst (lower) scanning rate mode. This can also be made to apply in thesecond scanning rate mode.

After a period of inactivity for an extended time period t4, duringwhich the sensing system has been scanning at the first rate, the systemcan be allowed to assume that there are no possible users in thevicinity of the dispenser. In such a case, even the time t1 may beconsidered too short to allow optimal power saving, and thus the systemcan alter the scanning rate to the third scanning rate lower than thefirst scanning rate, during which a scanning pulse is issued only onceafter elapse of time t3. However in such a case, when one IR signal isreceived which is at or above the predetermined level (e.g. 15% or moreabove background level), then the system should alter the scanning ratedirectly to the second higher scanning rate, rather than first adoptingthe original first scanning rate. However, in such a case it isappropriate to require at least two scans but preferably more scans tocause product dispensing. For example, when a washroom where thedispenser is placed is put into darkness, and then at some time laterthe lights are turned on, the IR received levels may be considered todetermine that a user is present. To avoid a product being dispensed insuch a case it may be appropriate to let the system have time to takeaccount of the background IR levels before being allowed to dispense.

In terms of the background level of IR, as mentioned above, this willvary over time. Likewise, the presence of fixed objects (e.g. soapdishes, other containers, or other fixed objects) within the range ofthe dispenser need to be taken account of as background IR. In order todo this, it has been found suitable to take a moving average of the mostrecently recorded IR received signals R so as to alter the level Q0 on acontinuous basis.

For example, the four (or more or less than four) most recently receivedIR signal values can be used to form the average value of backgroundsignal level by dividing e.g. the sum of the four most recent receivedsignal levels by four. As each new value of IR is received, the oldestvalue of the four values is moved out of the calculation (e.g. byremoving it from a register or store of most recent values in thecontrol circuitry) and calculating a new average based on the mostrecent values. Calculation of a moving average and the means required todo this in both hardware and/or software for the most recently recordedset of values is very well known in the art of electronics, and thus isdeemed to require no further explanation here.

By using such a moving average of background IR level, the furtheradvantage is obtained that when a user who has just withdrawn a towel orother product keeps his/her hands at the dispensing outlet, the receivedIR level will remain high. However, to prevent a user in this waycausing discharge of a large amount of product, e.g. paper towelmaterial, the user's hands will be regarded as being background IR whenthey are relatively stationary and thus dispensing will not occur. Todispense a further product (e.g. paper), the user must therefore movehis/her hands away from the dispenser sensors to allow a reading of“true” background IR (i.e. background IR without the user's hands beingpresent too close to the device). Only upon renewed movement of theuser's hands towards the dispenser sensors can product dispensing becaused to occur again.

A still further means by which misuse of a dispenser by repeatedwithdrawing of towels unnecessarily can be prevented is by arranging, inaddition or even as an alternative to the above moving average, anadjustable minimum elapsed time between towel dispensing (e.g. a time ofbetween 2 and 10 seconds). However, this feature is not generallyrequired since in most cases, the inherent elapsed time for the systemto determine a user as being present in the dispensing zone and to turnthe motor to dispense a towel, will be sufficient to prevent suchmisuse.

It will also be appreciated that as the batteries of the dispenserdischarge over time, the power supplied to the sensors may also beaffected, which may cause less efficient operation. To prevent this fromoccurring, and thus to ensure a stable voltage is available for supplyto the sensors (until a time close to total battery depletion), aconstant current sink may be employed. Such constant current sinks toprovide voltage stability are well known per se in the art ofelectronics, and thus are deemed to require no further description here,although it will be understood that their use in the sensing circuitryfor such a dispenser as described herein is particularly advantageous.The amount of extra energy required to operate the constant current sinkis negligible, and thus use of such a device is barely noticeable onbattery useable lifetime.

The power supplied to the emitters may additionally be arranged to bevaried by an automatic control, suitably between an amount of 0.001 mAsto 0.1 mAs (when using a 6V battery installation), in order to takeaccount of reflected signal strength from previous scans and to adjustthe level of emitted IR to a more suitable level.

This can be achieved by varying the current to the emitters between e.g.1 mA and 100 mA (i.e. a 100-times variation possibility). This can bedone by using the PWM module 106 (to be described later) whereby asquare PWM signal is converted to a DC voltage having an outputproportional to the PWM duty cycle, and whereby the MCU changes the PWMduty cycle to adjust the DC voltage to the emitter circuits, and thusthe power of the IR signal emitted, based on signal strength inputsreceived by the sensors and sent to the MCU. For example, if thereflected signal strength is very low on the last few scans (e.g. fivescans) when dispensing occurred, this may be because the typicalbrightness of the user's hands is low and background light levels arerelatively high. This may cause received signal levels to be only justabove the predetermined level compared to background IR unless theuser's hands are placed very close to the sensors, which can lead todifficulty in detection in some circumstances. In such a case, it may besuitable to increase the power supplied to the IR emitters so as toreceive a more easily perceptible signal change. Likewise, if thetypical brightness of the user's hands is high and background IR levelsare low, it may be suitable to decrease the power supplied to the IRemitters as an easily perceivable signal level change (i.e. reflected IRlevel during dispensing compared to background IR level) is received. Inthis way, the power supplied to the emitters is still further optimizedto take account of such conditions while providing reliable and fastsensing and dispensing. Thus, apart from in very high light conditions,only very low power to the sensors can be used. In this way, it willalso be understood that the dispenser can be optimized such that thefirst detection zone in which the presence of a possible user causeschanging from the first to the second scanning rate is selected to lieat between about 20 and 60 cm, preferably between 25 cm and 50 cm fromthe discharge outlet. It will be apparent that further increases inpower to the emitters will increase the range of detection, but thepower consumption will increase at a much greater rate and falsedetections may also occur more easily. Thus the range of up to 50 cmfrom the dispenser for allowing detection of a user is a preferredmaximum.

An alternative, possibly simpler, method which can be used to vary theIR emitter current, rather than by comparing (as above) the values ofreflection to background levels, is to set a so-called “standard value”or “threshold value” in the control circuitry, which is a value of theexpected detected signal strength received in normal operatingconditions. The current supplied might be e.g. 5 mA. If this standardvalue is called A1, then during operation the control circuitry (MCUthereof) can be made to calculate the IR level, A2, from a predeterminednumber of the most recently received IR values (i.e. the moving averageof the most recent values). If A2>A1 (i.e. the detected reflectionmoving average signal level A2 is above the stored standard signal levelA1) the current supplied to the emitter can be reduced, preferably inincrements. Likewise, in the case where A2>A1, then the current suppliedto the emitters can be increased, preferably incrementally.

In a further preferred embodiment, the dispenser can be arranged to havetwo modes of operation, one being the sensing mode described previouslywhereby active IR sensing is operating, the other being a hanging towelmode whereby each time for example a paper towel is dispensed and alsoremoved (e.g. torn off), a new paper towel is discharged from thedispenser. For this purpose, the cutting edge 16 as shown in FIG. 2 forexample could be mounted such that the application of pressure againstthe cutting edge (often referred to as a cutter bar) causes a switch tobe actuated to start the motor M to issue a new piece of towel ready tobe torn off. The device may also include a manual switch so that thishanging towel mode can be set manually by a user, or automatically by atiming circuit, for example at known time periods when the dispenserwill normally be in constant use and the use of the active IR sensorsystem is temporarily superfluous.

A hanging towel mode can also for example be suitable in extremely highbackground IR conditions when the sensing system is totally saturated,and thus cannot detect the difference in the increased level of IRradiation from a user compared to background levels, or at times closeto battery depletion when the power consumption of the active IR sensingsystem is unsuitably high for the remaining power. An automaticswitching to this mode and turning off the active IR sensing in times ofvery high background IR (e.g. at or above 10000 lux) and batterydepletion may thus also have advantages.

FIG. 6 shows a block diagram of the basic system of one embodiment of adispenser according to the invention, in which the portion shown indotted lines includes the basic components for IR signal modulation, IRemission and IR reception used to submit a sensing signal to the A/Dmodulation of the master control unit (MCU) which unit contains amicroprocessor.

Box 101 and 102 denote IR emitter(s) and receiver(s) respectively,corresponding generally to the previously described emitters 10, 12 and9, 11, 13. These IR emitters and receivers are preferably photodiodesThe user's hand shown outside the dotted lines indicates that IRradiation emitted by the emitter(s) 101 Is being reflected by the handback to receiver(s) 102. Unit 103 is a photoelectric converter forconverting the received IR signal before it is passed to filtering andamplification unit 104 where the band pass filter and amplificationcircuits operate to amplify the received signal around the centralfrequency in a limited band width and to thereby suppress other IRfrequencies relatively. The signal is then passed to a signalrectification unit 105, since the IR signal is an AC signal. From theunit 105, the signal passes into the A/D module 113 of the MCU.

For IR signal emission, an analogue pulse width module 106 is used tocontrol the power of the IR emission. The output of the PWM module 106is controlled by the MCU such that a square wave signal from the PWM canhave its duty cycle varied by the MCU to adjust the DC voltage to theemitter circuits and thus the power of the IR signal emitted. The PWM106 is connected to a D/A converter 107 and into an IR emitter drivingcircuitry unit 109 which includes the constant current sink mentionedpreviously. Into the same IR emitter driving circuitry is also fed asignal from a phase frequency detection module 108 which issues a 15 kHz(±0.5%) impulse modulated signal (or another frequency of modulatedsignal as considered appropriate) so as to drive the emitters 101 viathe emitter driving circuitry 109 to emit modulated IR signals for shortintervals (e.g. each signal is emitted for about 1 ms). In this regardit should be noted that before the modulated signal is emitted, the MCUshould first have already put the filter and amplification circuit unit104 for the received signal into operation for a short period, e.g. 2.5ms, before emitting a modulated pulse, so as to allow the receivercircuit to stabilize so as to reliably detect reflected IR from theemitted IR signal. Since the unit 104 is already in operation when theIR scanning pulse is emitted and since the filters and amplificationunit are centered around the central frequency of the emitted pulse,there is no need to synchronize the timing of the emitted pulse and thereceived pulse to any further extent.

The signal from unit 109 feeds into the IR emitter on/off control unit110. The input/output module 118 of the MCU also feeds into the unit 110to be turned on and off as required to thereby perform an IR scan viathe emitter 101.

In order to activate the microprocessor (i.e. wake it up to perform ascan at a certain rate), RC wake-up circuitry 115 feeds into the MCUinto a wake-up detection unit 114. Unit 117 is an external interruptdetection unit.

From the input/output module 118 is a feed to unit 119 which can beregarded as the motor driving circuitry which drives the motor M whenthe sensor system (which preferably includes the MCU and software) hasdetected that a product should be dispensed due to the determination ofthe presence of a user in the dispensing zone.

Further peripheral units 111, 112 are respectively a paper sensingcircuit unit and a low power detection circuit (i.e. for detectingbatteries close to depletion) input to the A/D module 113 of the MCU.Unit 116 indicates battery power which is used to drive the MCU and alsoall other peripherals and the motor. Unit 120 may he motor overloadcircuitry which cuts off power to the motor for example when paperbecomes jammed in the dispenser or when there is no paper in thedispenser. Unit 121 is a paper length control unit, which operates suchthat a constant length of paper (which is itself variably adjustable bymanual operation e.g. of a variable resistor or the like) each time themotor is made to operate to dispense a length of paper sheet 7 throughthe discharge opening 3. This unit 121 may also include a low powercompensation module by which the motor under lower power is made to turnfor a longer period of time in order to dispense the same length ofpaper sheet, although the unit may simply be a pulse position controlsystem, whereby the rotation of the motor is counted in a series ofpulses and the rotation is stopped only when the exact number of pulseshas been achieved. Such a pulse position control system could includefor example a fixedly located photointerruptor, which can detect slotsin a corresponding slotted unit fixed to the motor drive shaft (oralternatively on the drive roller 5 operably connected to the drivemotor) . Unit 122 may be low paper detection circuitry and unit 123 maybe a unit used to indicate whether the casing is open or closed. Thiscan for example be used to provide automatic feeding of a first portionof paper from the paper roll through the discharge opening when the caseis closed, e.g. after refilling with a new roll of paper, so that theperson refilling the dispenser is assured that the device is dispensingproperly after having been closed.

Although not shown here, a series of warning or status indication lightsmay be associated for example with various units such as units 111, 112,120 to 123 to indicate particular conditions to a potential user,dispenser attendant or repairman (e.g. if the dispenser motor is jammedor the dispenser needs refilling with paper or the like).

FIG. 7 shows one embodiment of an RC control circuitry which can be usedto give a timed wake-up of the microprocessor in the MCU. The principleof such a circuit is well known and in the present case, a suitablevalue for the resistor Re is 820 kOhm and for the capacitor 0.33microfarads. Although not shown specifically in FIG. 6, the RC wake-upcircuitry uses the input/output unit 118 of the MCU to provide the timedwake-up function of the microprocessor so that a scan occurs at theprescribed time interval (t1, t2 or t3 for example). When there is ahigh to low voltage drop at the input/output, as a result of the RCcircuitry, the MCU will “wake-up” and perform a scan. This wake-upleading to the performing of a scan also requires supporting software.Likewise, the length of the time t1 and/or t2 and/or t3 can suitably bemade as a multiple of the RC circuitry time constant, whereby the inputfrom the RC circuit can be used in the software to determine whether ascan is required or not at each interval. In this regard, it will benoted that an RC circuit is subject to voltage changes at the input (viaVDD which is the MCU supply voltage source acquired after passingthrough a diode from the battery voltage supply). As the voltage of thebattery (or batteries) drops, there will then be an increase in the RCtime constant in the circuit of FIG. 7, and thus the times t1, t2 and t3set initially will vary as the batteries become more depleted. Forexample, with the time t1 set at the preferred level of 0.17 seconds fora battery level of 6V, a drop to depletion level of 4.2V will increasetime t1 to 0.22 s. Thus, the values of t1, t2, t3 etc., as used herein,are to be understood as being the values with a fully charged batterysource.

FIG. 8 shows a modified RC circuit which has the advantage of using lesscurrent than the circuit shown in FIG. 7. In FIG. 8, three bipolartransistors are used to minimize the current used when the MCU isasleep.

Under normal conditions, the digital circuitry inside the MCU operatesin a logic High voltage state and a logic Low voltage state at which thecurrent drain is very low. However when the RS-wake-up circuitry isconnected as in FIG. 7 (whereby the indication “to MCU” implies aconnection to the input/output port of the MCU) this creates a voltagechange at the input/output port of the MCU which is a progressivevoltage change, due to the charging and discharging process in the RCcircuit. This creates a relatively long working period for the digitalcircuitry in the MCU, in turn resulting in an internally higher currentconsumption in the IC internal circuitry than is present during normaloperation conditions. This results in somewhat higher power consumptionto the MCU during its “off” cycle (i.e. the “sleep” cycle of the MCU).

By the circuitry in FIG. 8, the modification includes the use of twoinput/output ports PA7 (right hand side in the Figure) and PB7 (lefthand side in the Figure) to the MCU. The important aspect of thiscircuit is that two transistors Q2 and Q3 have been added in cascadewhich together modify the RC charge-up characteristics. The MCU PA7 pinthen gives a much sharper charge-up curve. The delay time constant forwaking up the MCU is determined by R4 and C1, which have been givenvalues of 820 kOhm and 0.68 μF respectively in the example shown. Othervalues for other time constants can of course be chosen.

The fast voltage change at port PA7 is achieved after conversion in Q2and Q3, which minimizes the time required for transition from a logicHigh voltage to a logic Low voltage level. Such a circuit as in FIG. 8can achieve about 40% power reduction during the sleep cycle compared tothe FIG. 7 circuitry for approximately the same RC time constants. Thus,the RC timing circuitry of FIG. 8 is particularly advantageous wheremaximum power is to be saved.

1. A dispenser for automatically dispensing a product stored in aproduct supply of said dispenser, said dispenser comprising: a sensorsystem for detecting the presence of a possible user to whom saidproduct may be dispensed, wherein said sensor system is arranged to scanfor the presence of a possible user at a first scanning rate, a secondscanning rate and a third scanning rate, and wherein said secondscanning rate is higher than said first scanning rate and said thirdscanning rate is lower than said first scanning rate, and wherein thesensor system is arranged to change said scanning rate from said firstscanning rate to said second scanning rate when a possible user isdetermined as having been detected by said sensor system to be within afirst detection zone, and said sensor system being arranged to changesaid scanning rate to said third scanning rate, when the sensor systemhas not detected the presence of a possible user for a predeterminedtime period.
 2. The dispenser according to claim 1, wherein said firstdetection zone includes an area which is located a further distance awayfrom the dispenser than a dispensing zone, and wherein the sensor systemis arranged such that a possible user determined by the sensor system ashaving entered the dispensing zone causes said dispenser to dispensesaid product.
 3. The dispenser according to claim 1, wherein saiddispenser is a paper dispenser.
 4. The dispenser according to claim 1,wherein said product supply includes a supply of non-perforated paper,and wherein said dispenser comprises a discharge outlet with a cuttingedge located proximate said discharge outlet and against which cuttingedge said paper may be moved relatively, so as to cut said paper forremoving a cut-away portion.
 5. The dispenser according to claim 4,wherein said dispenser includes a housing comprising said dischargeoutlet.
 6. The dispenser according to claim 1, wherein said dispenser isa paper hand-towel dispenser, and wherein said product supply is in theform of a continuous sheet of paper.
 7. The dispenser according to claim1, wherein the sensor system comprises infrared sensors, including atleast one infrared emitter and at least one infrared receiver arrangedat a discharge outlet of said dispenser.
 8. The dispenser according toclaim 7, wherein the sensor system comprises at least two infraredemitters and at least three infrared receivers for detecting presence ofa possible user.
 9. The dispenser according to claim 8, wherein in alateral direction of the dispenser discharge outlet, the receivers andemitters are arranged consecutively asreceiver/emitter/receiver/emitter/receiver.
 10. The dispenser accordingto claim 1, wherein the first scanning rate is a rate of between 0.15 to1.0 seconds between single scans, and said second scan rate is a rate ofbetween 0.05 to 0.2 seconds between single scans.
 11. The dispenseraccording to claim 1, wherein the first scanning rate is a rate of 0.15to 0.4 seconds between single scans, and the second scanning rate is arate of 0.05 to 0.15 seconds between single scans.
 12. The dispenseraccording to claim 1, wherein said predetermined time period is a timeof at least 60 seconds.
 13. The dispenser according to claim 1, whereinsaid sensor system comprises a further sensor arrangement including atleast one emitter and one receiver arranged to detect the presence of apossible user at a distance of more than 50 cm.
 14. The dispenseraccording to claim 13, wherein said sensor arrangement is located in thedispenser at an external surface thereof, so as to face forwardly andoutwardly on an outwardly facing frontal portion of said dispenser sothat portions of at least the emitters of the sensor arrangement projectexternally from said dispenser.
 15. The dispenser according to claim 13,wherein said further sensor arrangement is arranged at a location remoteto said dispenser and operably connected to said dispenser sensingsystem by means of a wire link or a wireless link.
 16. The dispenseraccording to claim 1, wherein said sensor system includes a controlsystem arranged to detect a possible user in dependence upon signalstrength of received infrared emissions, such that a possible user isdetermined to have entered said first zone when said sensor systemdetects a change in received signal strength which is greater than apredetermined amount above another signal strength level, said change insaid received signal strength level being a predetermined signalstrength level above a background signal strength level.
 17. Thedispenser according to claim 16, wherein a possible user is determinedto have entered a dispensing zone when said sensor system is operatingat said second scanning rate and when said control circuitry detects asignal strength greater than a predetermined signal strength levelcompared to background signal strength level for a predetermined numberof single scans at said second scanning rate, thereby causing saiddispenser to dispense a product.
 18. The dispenser according to claim16, wherein said predetermined signal strength level is 10% higher thanbackground level.
 19. The dispenser according to claim 16, wherein saidpredetermined number of single scans at said second scanning rate isbetween one and five scans.
 20. The dispenser according to claim 16,wherein said control system is arranged to regard a user as havingentered the dispensing zone when the received signal strength in onesingle scan at either the first or second scanning rates is 30% or moregreater than the background signal level.
 21. The dispenser according toclaim 1, wherein said second scanning rate is maintained for apredetermined time period after said control system has caused saiddispenser to dispense a product, before reverting back to said firstscanning rate.
 22. The dispenser according to claim 1, wherein saidsecond scanning rate is maintained for a predetermined number of scansafter said control system has caused said dispenser to dispense aproduct, before reverting back to said first scanning rate.
 23. Thedispenser according to claim 1, wherein said sensor system changes saidsecond scanning rate back to said first scanning rate immediately afterthe sensor system has registered that a product is to be dispensed. 24.The dispenser according to claim 1, wherein said sensor system isarranged to emit infrared radiation only with a first limited emittingfrequency band and wherein said sensor system is arranged to detectradiation in a limited frequency detection range of between about 2 to10 kHz bandwidth both above and below said first emitting frequencyband.
 25. The dispenser according to claim 24, wherein said firstemitting frequency is about 15 kHz and said frequency detection range isbetween about 12 kHz and 18 kHz.
 26. The dispenser according to claim 1,wherein said sensor system is an infrared sensor system, wherein thepower supplied to one or more emitters of said sensor system isvariable, so as to be able to vary the emitted infrared signal strength.27. The dispenser according to claim 26, wherein the power supplied tosaid one or more emitters is increased when the average signal level ofa predetermined number of the most recently received previous scans isless than at least a first predetermined signal level, and wherein saidpower supplied is decreased when the average energy level of apredetermined number of the most recently received previous scans ismore than said first predetermined signal level.
 28. The dispenseraccording to claim 27, wherein the power supplied to said one or moreemitters is determined such that a possible user will cause a changefrom said first scanning rate to said second scanning rate when saiduser is located a distance of up to somewhere between 20 and 60 cm fromthe discharge outlet of said dispenser.
 29. The dispenser according toclaim 1, wherein said sensor system includes means for detectingbackground infrared radiation, said means includes a storage of apredetermined number of most recently received infrared detectionsobtained during scanning, and wherein an average of said predeterminednumber of most recently received infrared detections is taken as thebackground infrared radiation level.
 30. The dispenser according toclaim 1, wherein said dispenser includes a device for adjusting aminimum time between dispensing one product and dispensing the nextproduct.
 31. The dispenser according to claim 30, wherein said devicefor adjusting a minimum time between dispensing one product and the nextproduct can be set to zero, such that the time between dispensing oneproduct and the next is determined by a minimum reset time inherent inthe system.
 32. The dispenser according to claim 1, wherein thedispenser and sensor system are battery powered, by a battery located inthe dispenser housing.
 33. The dispenser according to claim 1, whereinat least the first scanning rate is set by an RC timing circuitoperating together with software controlled by a microprocessor, whereinsaid microprocessor is woken up by said RC timing circuit supplying acurrent to an input of the microprocessor at the end of each RC timeconstant, and which causes said microprocessor to be inactive betweenscans.
 34. The dispenser according to claim 33, wherein the RC timingcircuit includes three bipolar transistors, two being in cascade, andtwo connections to an input/output section of said microprocessor.